Fix bug in code transforming TextShape

crates/epaint/src/shapes/shape.rs

@@ -456,40 +456,7 @@ impl Shape {
                 rect_shape.blur_width *= transform.scaling;
             }
             Self::Text(text_shape) => {
-                let TextShape {
-                    pos,
-                    galley,
-                    underline,
-                    fallback_color: _,
-                    override_text_color: _,
-                    opacity_factor: _,
-                    angle: _,
-                } = text_shape;
-
-                *pos = transform * *pos;
-                underline.width *= transform.scaling;
-
-                let Galley {
-                    job: _,
-                    rows,
-                    elided: _,
-                    rect,
-                    mesh_bounds,
-                    num_vertices: _,
-                    num_indices: _,
-                    pixels_per_point: _,
-                } = Arc::make_mut(galley);
-
-                for placed_row in rows {
-                    let row = Arc::make_mut(&mut placed_row.row);
-                    row.visuals.mesh_bounds = transform.scaling * row.visuals.mesh_bounds;
-                    for v in &mut row.visuals.mesh.vertices {
-                        v.pos *= transform.scaling;
-                    }
-                }
-
-                *mesh_bounds = transform.scaling * *mesh_bounds;
-                *rect = transform.scaling * *rect;
+                text_shape.transform(transform);
             }
             Self::Mesh(mesh) => {
                 Arc::make_mut(mesh).transform(transform);

crates/epaint/src/shapes/text_shape.rs

@@ -89,6 +89,63 @@ impl TextShape {
         self.opacity_factor = opacity_factor;
         self
     }
+
+    /// Move the shape by this many points, in-place.
+    pub fn transform(&mut self, transform: emath::TSTransform) {
+        let Self {
+            pos,
+            galley,
+            underline,
+            fallback_color: _,
+            override_text_color: _,
+            opacity_factor: _,
+            angle: _,
+        } = self;
+
+        *pos = transform * *pos;
+        underline.width *= transform.scaling;
+
+        let Galley {
+            job: _,
+            rows,
+            elided: _,
+            rect,
+            mesh_bounds,
+            num_vertices: _,
+            num_indices: _,
+            pixels_per_point: _,
+        } = Arc::make_mut(galley);
+
+        *rect = transform.scaling * *rect;
+        *mesh_bounds = transform.scaling * *mesh_bounds;
+
+        for text::PlacedRow { row, pos } in rows {
+            *pos *= transform.scaling;
+
+            let text::Row {
+                section_index_at_start: _,
+                glyphs: _, // TODO(emilk): would it make sense to transform these?
+                size,
+                visuals,
+                ends_with_newline: _,
+            } = Arc::make_mut(row);
+
+            *size *= transform.scaling;
+
+            let text::RowVisuals {
+                mesh,
+                mesh_bounds,
+                glyph_index_start: _,
+                glyph_vertex_range: _,
+            } = visuals;
+
+            *mesh_bounds = transform.scaling * *mesh_bounds;
+
+            for v in &mut mesh.vertices {
+                v.pos *= transform.scaling;
+            }
+        }
+    }
 }
 
 impl From<TextShape> for Shape {

crates/epaint/src/text/fonts.rs

@@ -617,7 +617,9 @@ pub struct FontsAndCache {
 
 impl FontsAndCache {
     fn layout_job(&mut self, job: LayoutJob) -> Arc<Galley> {
-        self.galley_cache.layout(&mut self.fonts, job, true)
+        let allow_split_paragraphs = true; // Optimization for editing text with many paragraphs.
+        self.galley_cache
+            .layout(&mut self.fonts, job, allow_split_paragraphs)
     }
 }